This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A232540 #12 Sep 08 2017 12:54:41 %S A232540 10,22,34,46,58,82,94,106,118,142,166,178,202,214,226,262,274,298,334, %T A232540 346,358,382,385,394,430,454,466,478,502,514,526,538,562,586,622,634, %U A232540 694,706,718,766,778,802,838,862,886,898,922,934,958,982,1006,1018,1042 %N A232540 Numbers n such that (n(n+1)/2) modulo sigma(n) = 1. %C A232540 Also numbers n such that antisigma(n) modulo sigma(n) = 1. Antisigma(n) = A024816(n) = the sum of the nondivisors of n that are between 1 and n, sigma(n) = A000203(n) = the sum of the divisors of n. %C A232540 Numbers n such that A232324(n) = 1. %C A232540 Number 5950 is only squareful number from first 1400 terms (< 50000) of this sequence. %C A232540 Conjecture: supersequence of A112774 (semiprimes of the form 6n+4). %H A232540 Jaroslav Krizek, <a href="/A232540/b232540.txt">Table of n, a(n) for n = 1..1000</a> %e A232540 106 is in sequence because antisigma(106) mod sigma(106) = 5509 mod 162 = 1. %t A232540 Select[Range[1100],Mod[(#(#+1))/2,DivisorSigma[1,#]]==1&] (* _Harvey P. Dale_, Sep 08 2017 *) %Y A232540 Cf. A000203, A076617, A024816, A112774, A232324, A232538. %K A232540 nonn %O A232540 1,1 %A A232540 _Jaroslav Krizek_, Nov 25 2013